Brake adjustment



Nov. 30, 1937. o. RAsMUssr-:N 2,100,488

BRAKE ADJUSTMENT Filed June 5, 193e 2 sheets-shawl ,b n 5W 947// W u we M M j/W/ /w w ff. 2 WW M/ M. M Mw n 4 .f5 Z., Wo/ fw #3 5\\ f. m

NOV. 30, 1937. Q RASMUSSEN 2,100,488

BRAKE ADJUSTMENT Filed .June s, 195e 2 sheets-sheet 2 Patented Nov.'30, '1937 l BRAKE ADJUSTMENT Olaf Rasmussen,

eral Motors Corporation, poration of Michigan Application June 3, 1936, Serial N0.

11 Claims. (Cl. 18S-79.5)

This invention relates to brakes, particularly to hydraulic brake applying means as used on vehicles. l

'Ilieobject ofthe invention is to provideimproved means to take up excessive clearances between the conventional drum and shoes and at the same time to maintain a predetermined clearance to accommodate variations in drum contour due to expansion, contraction and distortion.

A further object is to provide plish the major objects by a co cated and arrange protected from foreign matter. I

A still further object is the'accomplishment o f the above objects by a construction which shall be highly ecient yet'simple and comparatively I inexpensive. g y Other objects and advantages will be understood from the .description which follows.

On the drawings, Fig. 1 is atransverse section brake drum showing the invention associated with the shoe actuating means.

- Fig. 2 is a similar section of a modlied embcdiment. to the rotation of the g5 Fig. 2a is a sectional view, partly broken away,

as seen from line 2a-2a of Fig. 2.

Fig. 3 is a section on line 3 3 of Fig. 2.

Fig. 4 is a longitudinal section through the actuating means of Fig. 2.

Fig. 5 is a transverse section through the drum showing a further modiicatlon.

Fig. 6 is a similar section designed more particularly for a special kind of sealing means.

Referring to Fig. 1, numeral Il represents a um flange engaged by shoes I3 Detroit, Mich., a 'cor' engages the outer .usual brake-releasing the two shoes t '-position. 'I'he operation is o hold 10 of the plunger.

the pistons plunger 39 after in-Fig. 3. Also, there. wilLbe used a conduit like of Fig. 3 from a master cylinder (not shown) axially together an Vintermediate part of the cylinder as at 21.

sans

rotary movement thereof. brake application requires the spring plained, as will occur with excessive lining wear, the pin travels in the sl moves inwardly and spirally along the vplunger until the brakesare fully applied. lmovement of the plunger the clutch with it until the seat the movement. Thisvaxial movement provides a- 2.100.488 oFF-ICE Dayton, Ohio, assignor to Gencylinder. The clutch 49 is'engaged by the central washer 53 of the Bellevilieftype a snapped-in retainer which j periphery of the washer. A protecting boot of rubber 51 engages the cylinder 5l and plunger and excludes foreign matter. The spring 59 is connected to them in brake-releasing When uid is forced through are spread apart. Each Therefore, ii' effective axial movement of 53 is stressed as exot and' the kclutch 49 For permitting the escape of air there is a small predetermined maximum clearance for the gap opening 29. This will be normally closed by a between the drum and shoes, which clearance 45 screw plug 3| vof Fig 3 Since no invention is is necessary to accommodate changes in the drum whichr isv nec drum contour is the axial movement of Fig. 2 shows gagedby shoes I I3 that the clearance between.v the shoe pressure. It will be seen anddrumi essary to accommodate changes .in

provided and is measured by .5o

a somewhat modified iorm. this embodiment the drum vIl isi'rictionally en and i l5 having .facings H1. 0o

Y rods |5|, the heads Ain' this application. A plunger Backing plate ||0 carries hydraulic wheel cylinder |2|. The pistons |33 are slidably mounted in the cylinder and have a preferred form of seal to prevent leakage, which seal is not claimed |31 transmits the pressurefrom the piston to the web of the shoe, the plunger being non-rotatable because of its bifurcated end |39. A suitable boot is shown'at |4|. Relative rotary movement. between the piston |33 and plunger |31 is prevented by the slot |40 in the former and the flattened end |38 of the latter.

Centrally of the cylinder is a centralizer or block |43 provided with axial grooves such as |45 and |41 to permit escape of air from and inlet of liquid to the chambers adjacent the piston. Into groove |41 extends an apertured bushing |49. The bushing locks the block |43 in the cylinder |2| and its aperture is for the passage` of the hydraulic medium. The pistons |33 are centrally threaded at |49 to receive thethreaded e |53 of which are located closely adjacent each other and have clutch teeth |55 for mutual engagement. The clutch elements of the heads are biased for mutual engagement by Belleville spring washers |51 engaging the heads |53 and snap rings |59 secured to the blockl43.

The figures show the parts in the positions they occupy when the brake is released. The

teeth |55 are mutually engaged. When fluid under pressure enters through .conduit 25 and groove |41 to the region adjacent the pistons |33, the pistons are moved toward the ends of the cylinder. The clearance between the shoes and the drum is iirst taken up and thereafter frictional drag is effected. While the clearances are being taken upthe rods |5| are carried; along with the pistons, the clutch teeth |55 separating." In doing so the springs |51 are stressed and when sufficiently stressed they operate to hold the rods |5| from reciprocation. Under such circumstances the rods rotate 1n the pistons to as-' sume new positions of inward adjustment. When the brake is released the lsprings |51 restore the rod heads |53 to clutch engagement and thus hold the piston in new positions somewhat outwardly from their former positions, whereby excessive clearance between .the shoes and drums cannot occur,` the clearance being always substantially that measured by the axial'movement of the heads |53. This clearance is sufficient to provide for such changes in drum contour as may be due to temperature and pressure eiects. Lining wear is compensated by the rotation oi rods |5| inthe pistons.

Still another ,form is shown by Fig. 5. This form diiers from that of Fig. 1 mainly in that for the cone clutchthere is substituted a tooth clutch. In thisv gure the drum is engaged by shoes one of which is shown and marked |3. The cylinder 2|| is mounted in the same way as is the cylinder 2| of Fig. 1. Within the cylinder there may be used the same pistons, one of which is shown at 33. Spring 3| is also used.` Plunger rod 239 has a bfurcated end 24| to engage shoe I3. It has a long lead groove 243 engaged by a pin 245 carried by the hub 241 extending'from a head 249, the latter having teeth 25| to engage cooperating teeth 253 on the inturned end of a member 255 secured to the end of the cylinder by a fastening clamp 251, the latter having one end part turned down into a channel 259 of the member 255 and its other end shaped to receive` mation marked 3|5:

as clearly shown.

the plunger adjacent its bifur- `of the other embodiments. The axial movement of head 249 prior to its rotation relative to plunger 239 as a measure of the shoe clearance to provide for changes in drum contour, and excessive clearance is automatically taken up by rotation of head 240 relative to the plunger. The teeth at Belleville spring 263 en- 25|`and 253 function as the equivalent of the cone clutch of Fig. 1.

In the several forms pistons, subsequent to adjustments to counteract lining wear, return to new positions of adjustment outwardly toward the ends of the cylinder. This has the effect of increasing the capacity of the system. The necessary added fluid will ordinarily be supplied from the reservoir because in such systems the retracted position of the piston in the master cylinder opens a passage to the reservoir. In certain wheel cylinders the sealing device is not in the form of a rubber cup carried by the piston but takes the form of a diaphragm which is carried by and closes the cavity of the cylinder but expands to push the piston. In such forms it may be desirable that the piston return to a predetermined position after brake application, regardless of the action of the take-up devices.

Fig. 6 shows a wheel cylinder of the type referred to in the above paragraph. The drum is engaged by shoes, one of which is marked |3. The cylinder includes an intermediate part 30| and end parts, one of which is shown at 303. The two, parts areA secured together by a fastening means 305 and, when so fastened, the parts clamp between them a iiexible expansible diaphragm 301. This diaphragm seals the hydraulic system .proper from the region traversedby the pistons. It should be understood that the. diaphragm shown is merely illustrative of that kind o! seal which is anchored to the cylinder rather than being movable with the piston. Since this kind of diaphragm isadapted after each brake applica-Z tion to return to its initial position because of itsA own inherent resiliency, it may be thought best that the piston which it is designed to move should also return to its' initial position. The piston is marked 309 and is provided with a slot 3| to receive the end of screw means 305 wherebythe piston is guided in its reciprocation. A plunger 3|3 has an external helical grooved for- The plunger has a forked end 3|1 to engage the web of shoe |3. A rubber boot 3|9 engages over `theend of the cylinder and around the plunger to prevent the entrance of foreign matter. A conical clutch 32| engages a conical seat 323 on the inner wall o! the cylinder. The clutch'32l has a toothed connection as at 325 with the threaded surfaceof the plunger. A spring 321 and retainer 329 .correspond in structure and function with and 55 'of Fig. similar spring 33| and retainer 333, the spring biasing a cone clutch 335 into contact with a cooperating conical face on the piston. The clutch has a threaded connection with the plunger.' The inner end o! the plunger is bored out to receive a spring 3 31 seated therein and engaging the piston With this embodimen by buiging the diaphragm the brake is applied 301 which pushes the already described, the

parts 53 1. The end of the piston carries a piston, the latter operable through the clutch 33B and its threaded connection with the plunger to move the latter and apply the brake. The normal clearance is determined by the axial movement of clutch 32| jointly with the plunger as before. When the brake is released after'any correction/for lining wear made by a rotary move- -The threaded connection -ment of clutch 32| aiongthe plunger, the piston 308 would not return to its the clutch is available to immediately advance the rod and'apply the brake as before.

I claim:

1. In a brake, aidrum, a shoe to .engage the drum, actuating means including reciprocable piston and'plunger parts to move said shoe, iirst clutch means having a threaded engagement with one of said parts whereby said rst clutch means is adiusted axially of the actuating means, and

second clutch means adapted to be disengaged from the first clutch means to permit a .limited joint movement of the said plunger part and thel rst clutch means and engage the rst clutch means to limitthe retracting movement of` the shoe and actuating-means.

2. The invention defined by claim l, said clutch means having conical engaging faces./ 3. The invention dened by claim 1, said threaded engagement comprising a helical groove in` said plunger, saidiirstclutch members havtive rotation r piston land shoe, a threadedconnection `ing a part traversing said groove. ,-f 4. The invention -deilned by claim 1 together with yielding means biasing said clutch means to clutch engaging position and stressed under'the iniiuence of joint axial movement of said iirst andactuating means prior to relaclutch means of said iirst clutch means and actuating means when the iirst clutch means becomes spring loaded.

5. In a brake, a drum, a shoe, acylindena piston movable therein, a plunger between the rst cone clutch having a with the plunger to change its position axially thereof, said cylinder shaped to form a second and cooperatingcone clutch. and yielding means carried .by the cylinder and stressed by Joint movement axially of the plunger and rst cone clutch whereby thereafter further axial movement of the first cone clutch is prevented and the first cone clutch is rotated about and by the movement of the plunger to change its Aposition axially of the plunger and to change the release position of the shoefupon brake release.

' .6. 'I'he invention deined by claim 5 together with a clutch device between the piston and plunger adapted to lock said, piston and plunger during the working stroke of spring to restore said piston to clutch adapted to release and to assume new p'osii-.ions axially of said plunger during such resmechanism providing for the latter and a a predetermined initial position` after brake application, said -7. In a brake.a drum, a shoe, a cylinder. a piston reciprocable therein, -a plunger between the piston and shoe, clutch means between the cylinderand plunger, means limiting the movement of the clutch means axially of the cylinder,

' said clutch means having 'a threaded connection with the plunger whereby the active stroke of the piston rst releases the clutch member by a joint axial movement and thereafter causes a relative displacement of the clutch member axially ofthe plunger to establish a new release po- .vsition of the shoe and plunger.

8.. 'I'he invention de'ned by claiml 7 together with a spring between the plunger and piston to restore the latter-to a predetermined initial position, a clutch between the piston and plunger through which all axial brake applyingmovements of the pis'ton'are transmitted to the plunger, said last-named clutch adapted to be released and shifted axially of the plunger during restoration of the piston as aforesaid.

9. In a brake, a drum, a shoe, a cylinder, a piston reciprocable therein, a plunger between the piston and shoe, a rod threaded in said piston, said rod having a head disposed centrally of the cylinder and shaped to constitute a clutch element, a cooperating clutch element,l mechanism providing for said head a yieldingly resisted limitedaxialv movement whereby when said piston is advanced the rod moves jointlytherewith and releases the clutch in the process of taking up brakev clearance and thereafter, when the limit of movement of the head is reached, the rod is rotated to new positions of axial adjustment relative to the piston to determine new release positions for the shoe and plunger.

10. In a brake, a drum, shoes, a cylinder within said drum, a plurality of pistons therein, means to admit uid under pressure between said pistons, plungers between said pistons and shoes,`

rods axially threaded in said pistons, said rods having heads located adjacent each other vnear rthe middle of the cylinder in brake release position,` said lheads having clutch elements for mutual engagement in brake release position, and each of said heads a yieldingly resisted limited axial movement whereby when the pistons are separated by the admis-l sion of pressure fluid the rods first travel jointly witl the pistons and the clutchis disengaged and thereafterfor movements of the pistons in excess of the limited movement provided for said heads the rods are rotated relative to the pistons to eilect new release positions for` the shoes and operating parts.

l1. In a brake, a drum, shoes to engage the drum, a cylinder within the drum, opposed pistons in thecylinder, plungers between the pistons and shoes, a hollow block secured to said cylinder between said`pistons, rods threaded in said pistons and having heads in said block, said heads ha gv opposed clutch teeth adapted for mutual engagement, mechanisms carried by said block to provide a limited resiliently resisted axial movement of said rods together with said pistons to cause declutching of said heads, said rods thereafter being rotated to changed positions of 1 adjustment axially of said pistons under continled piston movements to effect new release positions for the shoes and brake operating parts.

l OLAF RAsMUssEN. 

